A round of ammunition for small arms or a light firearm typically comprises a case and a projectile. The case has one end which is crimped onto the projectile. An opposite end of the case is formed with a planar base wall that seats a primer. A volume of propellant is held within the cartridge between the projectile and an inside of the planar base wall. When the ammunition round is used, the primer is initiated usually mechanically by striking with a firing pin. This in turn causes deflagration of the propellant. Deflagration of the propellant results in the rapid generation of a large volume of gas. This gas expels the projectile from the case and propels the projectile through the barrel of the small arms or light firearm. The case may be expelled either automatically or manually. Ammunition has also been proposed which does not comprise a case. This is sometimes known as caseless ammunition. An example of such ammunition is set out in U.S. Pat. No. 2,307,369 (Ferrel). This discloses a round of ammunition comprising a caseless projectile having a body defining a cavity which is filled with a propellant charge. One end of the projectile is closed by an integral nose while an opposite end is closed by a firing cap. A soft metal jacket or sleeve is applied to the exterior of the projectile. The jacket is provided with shoulders that are configured to: engage with rifling of a barrel of a firearm; or, seal against the bore of a smooth bore firearm from which it is fired.